Gasifier structure

ABSTRACT

A gasifer comprising the size of an opening of the furnace less than the size of a bottom of the furnace, representing the narrow top and wide bottom furnace, with a heating system surrounding around the outer peripheral of the furnace. A heating is performed on the solid ion source. As continuously reducing the solid ion source during the heating, the surface area of the solid/ gaseous interface effectively offsets the reduction of the total amount obtained by the ion implater due to the reduction of the solid ion source.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gasifier structure and, more particularly, to a gasifier which prevents the reduction of the total ion source obtained by the ion inplater in the gasifier from continuously gasifying the solid ion implater in the gasifier.

2. Description of the Prior Art

In all semiconductor devices, an ion implant is very important technology in the transistor structure. In the ion implantation process, the wafer is subjected to impact by the charge ion stream, which is the so-called dopant. When the doping obtains the sufficient energy, the thin film is implanted to a desired depth, thereby changing the property of the material and providing the specific electrical property. The ion implant accurately controls the dopant concentration in the doping area. The dopant solution (the dose) is controlled by the ion stream current (the total ion amount in the ion stream) and the scanning ratio (the times which the wafer passes through the ion stream). The depth of the dopant is determined by the energy magnitude of the ion stream.

However, the ion source in the ion stream is generally obtained from the solid ion source gasified in the gasifier. The structure of the conventional gasifier, as shown in FIGS. 1 and 2, greatly reduces the total solid source amount in the furnace 12 as gasifying the solid ion source in the furnace 12 of the gasifier. Thus phenomenon results in reducing the total gasified ion amount obtained by the ion impanter, In order to maintain a specified doping ion concentration, a manual operation is required to arise the temperature in the gasifier in order to accelerate the subliming speed of the solid ion source or re-adjust the ion stream current. Therefore, the throughput of the ion implater is loss.

In view of the above problems, the present invention provides a gasifier structure to overcome the disadvantages of reducing the solid ion source.

SUMMARY OF THE INVENTION

The present invention provides a gasifier structure, comprising the size of an opening of the furnace less than the size of a bottom of the furnace, representing the narrow top and wide bottom furnace, which prevents the reduction of the ion source obtained by the ion inplater in the gasifier from gasifying the solid ion implater, and which prevents the loss cost and time from the manual operation required to arise the temperature in the gasifier.

The present invention also provides a gasifier structure, comprising the size of an opening of the furnace less than the size of a bottom of the furnace, representing the narrow top and wide bottom furnace, thereby effectively preventing the greatly increase of the surface area of the solid/gaseous interface from the continuously sublimation of the solid ion source due to the heating, resulting in maintaining a total gasified ion amount obtained by the ion implater, in order to solve the disadvantage of re-adjusting the ion stream current.

To achieve the aforementioned objects and more, a preferred embodiment of the present invention provides a gasifier structure, comprising a furnace and a heating system, characterized by: the size of an opening of the furnace less than the size of a bottom of the furnace, representing the narrow top and wide bottom furnace.

These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

FIGS. 1 and 2 are cross-sectional views of a gasifier according to the prior art;

FIG. 3 is a cross-sectional view of a gasifier according to a preferred embodiment of the present invention; and

FIGS. 4 and 5 are the cross-sectional views of a heating system surrounding around the outer peripheral of the furnace according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer to FIG. 3, which shows a gasifier of the present invention, comprising the size of an opening less than the size of a bottom of the furnace, representing the narrow top and wide bottom furnace 14. The furnace 14 can be a conical shape or angle conical shape, and a heating system 16 is surrounded around the outer peripheral of the furnace 14.

In order to describe the present invention, a solid ion source with a shorter heating time of FIG. 4 and a solid ion source with a longer heating time of FIG. 5 will be respectively described in details hereinafter.

Refer to FIGS. 4 and 5, when a heating is performed on the solid ion source 18 in the furnace 14 by using the heating system 16 surrounding around the outer peripheral of the furnace 14, as continuously raising the temperature, a sufficient heat energy is performed to the solid ion source 18 to jump from the solid energy barrier and the liquid energy barrier, thereby directly subliming to a gaseous status. In this situation, all solid ion sources 18 in the furnace 14 are gradually reduced, thereby generating the subliming amount of the solid ion source 18 in FIG. 4 (defining the force as F1) greatly larger than the subliming amount of the solid ion source 18 in FIG. 5 (defining the force as F2). At this time, because the solid ion source 18 is reduced, the solid/gaseous interface of the solid ion source 18 is designed as the narrow top and wide bottom based on the shape of the furnace 14, thereby presenting the surface area (defining the surface area as A1) of the solid/gaseous interface as shown in FIG. 4 greatly less than the surface area of the solid/gaseous interface (defining the surface area as A2) as shown in FIG. 5, that is, A1≦A2.

If the heating time is shorter, as shown in FIG. 4, the ion implater obtains the total ion amount which is F1×A1. If the heating time is longer is longer, as shown in FIG. 5, the ion implater obtains the total ion amount which is F2×A2. At this time, F1×A1≈F2×A2. Since the size of an opening of the furnace is less than a size of a bottom of the furnace, A2 is greatly larger than A1, thereby supplementing a situation which F2 is greatly less than F1.

The present invention provides a gasifier which a furnace structure is represented by the size of the opening less than the size of the bottom, in order to effectively offsetting the greatly sublimation of the solid ion source caused by the furnace having the same width on the top and the bottom due to the sufficient heat energy, and in order to effectively offsetting the greatly reduction of total ion amount obtained by the ion implater as reducing the solid ion source, thereby preventing the re-adjustment of the electron beam from the conventional technology, and preventing the throughput reduction from arising the temperature in the gasifier to obtain an identical total ion amount.

The embodiment above is only intended to illustrate the present invention; it does not, however, to limit the present invention to the specific embodiment. Accordingly, various modifications and changes may be made without departing from the spirit and scope of the present invention as described in the following claims. 

1. A gasifier, comprising: a furnace; and a heating system surrounding around the outer peripheral of the furnace; characterized by: a size of an opening of the furnace less than a size of a bottom of the furnace.
 2. The gasifier of claim 1, wherein the furnace is shaped of a cone.
 3. The gasifier of claim 1, wherein the furnace is shaped of an angle cone.
 4. The gasifier of claim 1, wherein the heating system is a resistive heating system. 